Question

Sodium acetate has a pH of 7.
A) True
B) False

Answer 1

Hint: the sodium acetate $\text{ C}{{\text{H}}_{\text{3}}}\text{COONa }$ is a salt that is formed by the reaction of acetic acid $\text{ C}{{\text{H}}_{\text{3}}}\text{COOH }$ and sodium hydroxide$\text{ NaOH }$. The acetic acid is a weak acid and sodium hydroxide is a strong base. The $\text{ pH }$of the salt depends on the neutralising power of acid and base.

Complete step by step answer:
According to Lowry –Bronsted acid base theory, the acid is a substance that tends to donate a proton to any other substance, and the base is defined as the substance which tends to accept the proton from the other substance.
The acid and base interact with each other and generate salt. The salt is an ionic compound.
Let's consider a weak acid acetic acid$\text{ C}{{\text{H}}_{\text{3}}}\text{COOH }$. It is a weak acid. The weak acid undergoes the dissociation in water as follows,
\[\text{ }\begin{matrix}
   \text{C}{{\text{H}}_{\text{3}}}\text{COOH} & + & \text{NaOH} & \rightleftharpoons & \text{C}{{\text{H}}_{\text{3}}}\text{CO}{{\text{O}}^{-}}\text{N}{{\text{a}}^{\text{+}}} & + & {{\text{H}}_{\text{2}}}\text{O} \\
   (\text{Acetic acid)} & {} & (\text{Sodium hydroxide)} & {} & (\text{Sodium acetate)} & {} & {} \\
\end{matrix}\text{ }\]
The acetic acid is a weak acid. It has a dissociation constant value equal to $\text{ }1.8\text{ }\times \text{ 1}{{\text{0}}^{-5}}\text{ }$. The acetic acid when treated with a strong base, sodium hydroxide $\text{ (NaOH) }$.
The acid reacts with the base to generate the salt. Here, the acetic acid reacts with sodium hydroxide to produce sodium acetate\[\text{C}{{\text{H}}_{\text{3}}}\text{CO}{{\text{O}}^{-}}\text{N}{{\text{a}}^{\text{+}}}\], which is a salt of acetate ion.
According to Lowry –Bronsted theory, the acid has a conjugate base. The acetic acid which is a weak base loses the proton to give a conjugate base, acetate ion. It is a stronger base.
It is a conjugate base of a weak acid. Thus it is a stronger base.
Thus, we can say that sodium acetate is a basic salt.
Now, we know that $\text{ pH }$ of the basic solution is always greater than the 7.
Since sodium acetate \[\text{C}{{\text{H}}_{\text{3}}}\text{CO}{{\text{O}}^{-}}\text{N}{{\text{a}}^{\text{+}}}\] is a basic salt it has a $\text{ pH }$ value greater than the 7.
Therefore, the given statement Sodium acetate has a pH of 7 is a false statement.

Hence, (A) is the correct option.

Note: Note that, the acidic salt, for example, $\text{ N}{{\text{H}}_{\text{4}}}\text{Cl }$has a $\text{ pH }$value less than the 7. The acidic salt is the conjugate acid of a weak base. If the strong acid and strong base interact with each other , they neutralises each other and forms a neutral salt which has the $\text{ pH }$value equal to 7.Thus, to form acidic salt one needs a weak base, and to generate basic salt, we require the weak acid.